1. Field of the Invention
This invention relates to centrifugal pellet dryers that are utilized to dry plastic pellets that have been cut from strands of plastic in a pelletizer. A water slurry of plastic pellets is introduced into the dryer where the pellets are separated from the water. The dry pellets can then be conveyed to a shipping container or to a location to be reprocessed.
2. Description of the Prior Art.
Centrifugal pellet dryers are well known in the art. Examples of centrifugal pellet dryers appear in U.S. Pat. No. 4,896,435 issued Jan. 30, 1990 and in U.S. Pat. No. 5,265,347 issued Nov. 30, 1993. In these patented pellet dryers, a slurry of pellets and water is introduced into the bottom of the dryer and a rotor carries the pellets and water upwardly through the dryer as the water is forced outwardly by centrifugal force through a cylindrical screen that surrounds the rotor. The pellets are removed near the top of the cylindrical screen and the water is drained from the bottom of the dryer housing.
In the above-described centrifugal pellet dryers and in earlier centrifugal pellet dryers, the slurry of pellets and water is introduced between the rotor and the cylindrical screen so that the rotor breaks the stream of the slurry where it is introduced and a large portion of the pellets is deposited on the screen near the entry port of the slurry stream.
In the present invention, the slurry stream of pellets and water is introduced through the rotor of the centrifugal dryer into the interior of the cylindrical screen or mesh member. By introducing the pellets and water through the rotor as the rotor rotates, the pellets and water are evenly distributed about the interior of the cylindrical screen or mesh member as opposed to a bottom feed where most of the initial dewatering is done in the first quadrant adjacent to the slurry inlet which loads up the screen and limits its effectiveness in the initial dewatering stage. The feed of the slurry through the rotor minimizes radial bearing loads that are present in the prior an since the lifter blades in the prior art must break the stream of water and pellets in one location that is off center from the rotor axis. The feed of the slurry through the rotor also enhances the centrifugal force of the rotor to force the water radially through the screen to thereby enhance the initial dewatering stage of the dryer.